1. Field of the Invention
The present invention relates to a pattern forming method using self-assembly and a method of manufacturing a structure by use of the pattern forming method. The processing method of the present invention can be used to manufacture high-density recording media and highly integrated electronic components, for example,
2. Background Art
Recent significant improvement in function of information appliances such as personal computers benefits greatly from the advance of fine processing technology used to manufacture semiconductor devices and the like. Up to now, for example, a miniaturization in fabrication size of semiconductor devices has been pursued by means of wavelength reduction in the source of exposure light mainly used in lithography. However, the higher the pattern density because of a further miniaturization in fabrication size, the higher the cost required for the lithography process in the manufacturing process. In next-generation semiconductor devices or high-density recording media manufactured through the use of fine processing, such as patterned media, a miniaturization in pattern size to 100 nm or less is required. For this purpose, use of an electron beam or the like as the exposure light source is expected. However, for the purpose of writing fine pattern, the amperage is typically reduced for a reduction in beam diameter of the electron beam. As a result, a writing sensitivity, namely, a writing speed decreases. The serious problem of a reduction in patterning throughput is left unsolved.
Against the background of the circumstances as described above, pattern forming methods have been proposed as a processing method capable of accomplishing a high throughput at low costs, which take advantage of phase separation structure of self-assembling block copolymer (see Appl. Phys. Lett., vol. 68, p. 2568 by P. Mansky et al., and Science, vol. 276, p. 1401 by M. Park et al., for example). In these methods, a polymer phase constituting a part of the phase separation structure of a block copolymer is removed through ozone treatment, plasma etching, electron beam irradiation or the like to create relief pattern. Then, the relief pattern is used as a mask to process the base substrate. The method using block copolymers is capable of creating ordered array patterns by means of the very simple processes of dissolving the block copolymer in a suitable solvent for coating a work piece therewith. The pattern size is defined by the molecular weight of the block copolymer. Therefore, if the phase separation structure of a block copolymer is within a stable range, it is possible to reduce the molecular weight for a decrease in pattern size, and phase separation structure of 30 nm or less is also provided.
Typically, the phase separation structure of a block copolymer is polycrystalline structure including a region where molecular arrangements are random. Therefore, it is impossible to physically access the individual structures isolated from each other to fetch a signal. In a method proposed for solving this problem, relief pattern or chemical pattern is pre-created on a substrate to which a coating of block copolymer is to be applied, so that the array directions in the phase separation structure of the block copolymers a coating of which is applied to the pattern are in order. The inventors have also proposed the recording media using arrays of block copolymers in Japanese Patent Laid-Open Publication No. 279616/2002 which are herein incorporated by reference.
However, even in the case of employing the methods as described above, typically, polymer molecules are randomly folded and the directions of the molecular chains are also random. Therefore, when the polymer molecules are arranged along a wall face of a patterned groove formed in the substrate, a period of the ordered structure is less likely to become constant. Such ordered structure which is not constant often gives rise to a serious problem when the phase separation structure patterns of block copolymers are used to manufacture electron devices or recording media. For example, in the case of an application to the aforementioned patterned media, the ordered structure which is not constant causes jitter noises of a reproduction signal or deviations from a positioning mark, leading to impossibility of writing and reading records at a high S/N ratio.